In SONET/SDH systems, management channels DCCR/DCCM is used as IBC i.e. in band communication channels. Similarly, the management channels are GCC channels for OTN (optical transport networks) systems. These management channels are typically HDLC based and any proprietary protocol can be run over HDLC. Management channels that are based on other packet technology (Ethernet, IP, etc.) are also capable of running proprietary protocols, however not very common. In any SONET/SDH based system, the typical requirement will be to support at least one DCCR/DCCM per optical port for IBC.
SONET/SDH systems consist of more than 150 optical ports are not uncommon. To support one DCCR, 3 slots are needed in HDLC controller along with super channeling support to make HDLC controller to treat all these 3 time slots as single HDLC controller channel. To support 150 such DCCR channels, 450 slots are needed in TDM based HDLC controller.
FIG. 1A shows the timing diagram of mapping DCCR channel into TDM slots. Each DCCR contains 3 bytes of 64 kbps data each. One byte of DCCR occupies 1 TDM slot, thus 3 TDM slots are required to support one DCCR channel. To support 150 such DCCR channels we require 450 time slots.
TDM based HDLC controllers with more than 450 slots are not cost effective. Some of the processors come with inbuilt HDLC controllers and we may need to migrate to higher end processor or use another dedicated HDLC controller for just to support more no of DCCR/DCCM channels, which is not a cost effective solution. FIG. 2A shows the prior art system block, for mapping management channels into TDM slots.
The figures depict embodiments of the disclosure for purposes of illustration only. One skilled in the art will readily recognize from the following description that alternative embodiments of the structures and methods illustrated herein may be employed without departing from the principles of the disclosure described herein.